When a vehicle, and in particular a self-propelled vehicle, is required to run over ground having different surface states, it is desirable to be able to adapt the characteristics of its suspension to the surface state of the ground. Similarly, when it is desired to adapt the vehicle to different types of driving, it is desirable to adapt the characteristics of its suspension to the desired type of driving. The spring and shock absorber device of the invention applies particularly, but not exclusively, to the suspension of a high performance motor car for driving both on the road and on a race track.